The present disclosure relates to electronic latch circuits, and more specifically, to a voltage level-shifting electronic latch circuit.
Electronic circuits can operate on a range of supply voltages. For example, a supply voltage (VDD) may be 3.3V in a certain application, and may be 1.0V in another application. Digital circuits may respond to logic values represented by certain ranges of voltages (logic threshold voltages) within their operating voltage range. A certain family of logic circuits, for example, can respond to voltages that are above 66% of the circuit's supply voltage as a logic “1”. The same family of logic circuits can respond to voltages that below 33% of the circuit's supply voltage as logic “0”. Consequently, two different families of digital logic circuits that have different supply voltages may define their logic thresholds ranges using different voltage levels. A first logic circuit from a family that uses a first logic threshold range can have a need to communicate with a second logic circuit from a family that uses a second, different logic threshold range. Accordingly, a circuit at the interface between the first and second logic circuits that shifts the voltage levels used by one circuit to the voltages levels used by the other circuit enables the two circuits to communicate.
A latch is an electronic circuit that can be used to store a piece of electronic information (e.g. a logic value). The latch circuit captures or latches on to one of two stable states based on the input of one or more input/control signals. A latch circuit can maintain the latched state even after the input/control signals are removed. An electronic latch may be constructed from pairs of cross coupled inverters.
Logic circuits may use complementary metal-oxide-semiconductor (CMOS) transistors. CMOS transistors include n-channel field effect transistors (NFET) and p-channel field effect transistors (PFET).